Re: [patch 1/2] Touchscreen support for sharp sl-5500

From: Russell King
Date: Mon Jul 25 2005 - 11:15:02 EST

On Mon, Jul 25, 2005 at 11:02:43AM -0500, Dmitry Torokhov wrote:
> On 7/25/05, Russell King <rmk+lkml@xxxxxxxxxxxxxxxx> wrote:
> > On Mon, Jul 25, 2005 at 10:16:05AM -0500, Dmitry Torokhov wrote:
> > > If the problem is that you have a single piece of hardware you need to
> > > bind several drivers to - I guess you will have to create a new
> > > sub-device bus for that. Or just register sub-devices on the same bus
> > > the parent device is registered on - I am not sure what is best in
> > > this particular case - I am not familiar with the arch.
> >
> > That is exactly the problem - these kinds of devices do _not_ fit
> > well into the device model. A struct device for every different
> > possible sub-unit is completely overkill.
> >
> > For instance, you may logically use one ADC and some GPIO lines
> > on the device for X and something else for Y and they logically
> > end up in different drivers.
> >
> > The problem is that the parent doesn't actually know how many
> > devices to create nor what to call them, and they're logically
> > indistinguishable from each other so there's no logical naming
> > system.
> >
> Then we should probably not try to force them into driver model. Have
> parent device register struct device and when sub-drivers register
> they could attach class devices (like input devices) directly to the
> "main" device thus hiding presence of sub-sections of the chip from
> sysfs completely. My point is that we should not be using
> class_interface here - its purpose is diferent.

If you look at _my_ version, you'll notice that it doesn't use the
class interface stuff. A previous version of it did, and this seems
to be what the collie stuff is based upon.

What I suggest is that the collie folk need to update their driver
to my version so that we don't have two different forks of the same
driver in existance. Then we can start discussing whether things
should be using kthreads or not.

Russell King
Linux kernel 2.6 ARM Linux -
maintainer of: 2.6 Serial core
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